CA2673181A1 - Method and apparatus for drying a fibrous web - Google Patents

Method and apparatus for drying a fibrous web Download PDF

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Publication number
CA2673181A1
CA2673181A1 CA 2673181 CA2673181A CA2673181A1 CA 2673181 A1 CA2673181 A1 CA 2673181A1 CA 2673181 CA2673181 CA 2673181 CA 2673181 A CA2673181 A CA 2673181A CA 2673181 A1 CA2673181 A1 CA 2673181A1
Authority
CA
Canada
Prior art keywords
characterized
fibrous web
steam
apparatus according
drying zone
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA 2673181
Other languages
French (fr)
Inventor
Luiz Carlos Da Silva
Thomas Scherb
Peter Kahl
Frank Wegehaupt
Dieter Mueller
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Voith Patent GmbH
Original Assignee
Voith Patent Gmbh
Luiz Carlos Da Silva
Thomas Scherb
Peter Kahl
Frank Wegehaupt
Dieter Mueller
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to DE200610062234 priority Critical patent/DE102006062234A1/en
Priority to DE102006062234.0 priority
Application filed by Voith Patent Gmbh, Luiz Carlos Da Silva, Thomas Scherb, Peter Kahl, Frank Wegehaupt, Dieter Mueller filed Critical Voith Patent Gmbh
Priority to PCT/EP2007/064290 priority patent/WO2008077869A1/en
Publication of CA2673181A1 publication Critical patent/CA2673181A1/en
Application status is Abandoned legal-status Critical

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Classifications

    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21FPAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00Dryer section of machines for making continuous webs of paper
    • D21F5/18Drying webs by hot air
    • D21F5/182Drying webs by hot air through perforated cylinders
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21FPAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F11/00Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
    • D21F11/14Making cellulose wadding, filter or blotting paper
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21FPAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F11/00Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
    • D21F11/14Making cellulose wadding, filter or blotting paper
    • D21F11/145Making cellulose wadding, filter or blotting paper including a through-drying process
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21FPAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F3/00Press section of machines for making continuous webs of paper
    • D21F3/02Wet presses
    • D21F3/0272Wet presses in combination with suction or blowing devices
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21FPAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00Dryer section of machines for making continuous webs of paper
    • D21F5/20Waste heat recovery
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21FPAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F7/00Other details of machines for making continuous webs of paper
    • D21F7/008Steam showers
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21FPAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F9/00Complete machines for making continuous webs of paper
    • D21F9/003Complete machines for making continuous webs of paper of the twin-wire type

Abstract

In a method for drying a fibrous web, in particular a paper, paperboard or tissue web, in which method the running fibrous web is loaded with hot air in the region of a predefinable drying zone, the fibrous web is loaded with steam at least in regions within the drying zone. A corresponding drying apparatus is also described.

Description

Method and apparatus for drving a fibrous web The invention relates to a method for drying a fibrous web, especially a paper, cardboard or tissue web, whereby the moving fibrous web is treated with hot air in the area of a pre-definable drying zone. It further relates to a corresponding drying apparatus as well as to a machine for the production of a tissue web with such a drying apparatus.

A method of the kind described above which serves to produce a voluminous tissue web and in which a so-called belt press in conjunction with a hot air hood or, alternatively a steam hood is utilized to dewater a fibrous web to a certain dry content is already known from WO
2005/075737 Al. With tissue machines it is important to reduce the energy consumption especially during the drying process in order to achieve a pre-determinable dry content. On the other hand there is a requirement to increase the dry content at reduced energy consumption.

It is the objective of the current invention to cite an improved method, as well as an improved apparatus of the type referred to above with which the drying process -preferably for the above described method for the production of a tissue web - is optimized, especially in consideration of the energy requirement for dewatering the tissue web.

Regarding the method, this objective is met in that the fibrous web is treated, at least in some areas, with steam inside the drying zone.

Accordingly, hot air and steam are used in combination together for drying the fibrous web, preferably a tissue web.

The fibrous web is advantageously treated with steam within the first half of the total drying zone length, when viewed in direction of web travel.

In this arrangement the fibrous web is treated preferably with steam, at least at the beginning of the drying zone, when viewed in direction of web travel.

Viewed in direction of web travel, the fibrous web can initially be treated with steam and subsequently with hot air. According to an alternative practical arrangement it is however also possible to treat the fibrous web when viewed in direction of web travel initially with hot air, subsequently with steam and then again with hot air.

In certain instances it is advantageous if the fibrous web, viewed in direction of web travel is treated at least essentially over the entire length of the drying zone with steam.

According to an alternative practical arrangement of the inventive method it is however also possible to treat the fibrous web with steam, at least essentially only within the first half of the total length of the drying zone when viewed in direction of web travel, whereby in this case the fibrous web is treated with steam, preferably at least essentially over only the first half of the total length of the drying zone, viewed in direction of web travel.

According to an additional advantageous arrangement the fibrous web is treated with steam, at least essentially only within the first third of the total length of the drying zone, and moreover preferably at least essentially over this first third, viewed in direction of web travel.

In certain cases it is also advantageous if the fibrous web is treated with steam, at least essentially only within the first quarter of the total length of the drying zone, and moreover hereby preferably at least essentially over this first quarter, viewed in direction of web travel.

r t CA 02673181 2009-06-18 According to an additional alternative arrangement of the inventive method the fibrous web is treated with steam only at the beginning of the drying zone, viewed in direction of web travel.

It is preferred if the fibrous web is treated with hot air over the pre-determinable drying zone. At least in this instance the drying zone can be defined, at least essentially through the area in which the fibrous web is treated with hot air. In this case the fibrous web may be treated with steam, particularly inside and/or prior to this drying zone.

The fibrous web is advantageously treated at least in some areas simultaneously with hot air, as well as with steam, viewed in direction of web travel. Under simultaneous treatment it is to be understood that a respective area of the fibrous web is treated with hot air, as well as also with steam.

According to a useful practical arrangement the fibrous web can be carried through the drying zone together with a permeable fabric, especially a structured fabric or a TAD-fabric (TAD =
Through Air Drying). In this case, hot air or steam (as far as this has not yet condensed in the web) flow initially through the fibrous web, and subsequently through the permeable fabric.
The inventive combined hot air and steam treatment can therefore also be used, for example in a TAD drying process.

A preferred alternative arrangement of the inventive process distinguishes itself in that the fibrous web, together with at least one permeable fabric, especially a structured fabric is guided through the drying zone, whereby hot air or steam flow initially through the permeable fabric and subsequently through the fibrous web.

In the drying zone the fibrous web can hereby be covered advantageously by at least one additional permeable fabric, especially a press belt, whereby in this case hot air or steam flow initially through the additional permeable fabric or press belt, subsequently through the first permeable fabric or structured fabric and finally through the fibrous web.
Moreover, in the use of a press belt a type of belt press is created through which in addition to the mechanical pressure especially the inventive combined hot air and steam drying process is applied.

A dewatering fabric, especially a felt can additionally be run through the drying zone together with the fibrous web, whereby hot air or steam - as far as this has not condensed on the web, as previously mentioned - initially flow through the additional permeable fabric or press belt, subsequently through the first permeable fabric or structured fabric and the fibrous web and finally through the additional dewatering fabric.

Basically it is however also conceivable to subject the fibrous web in the drying zone at least in some areas to impingement drying. In this scenario therefore, the inventive combined hot air and steam application is used within the scope of such an impingement drying.

Basically however, the fibrous web may be subjected at least in some areas, also to through-air drying.

The objective mentioned at the beginning is solved inventively moreover by an apparatus for drying a fibrous web, especially a paper, cardboard or tissue web, including a drying zone where the moving fibrous web can be treated with hot air and whereby this apparatus is characterized in that the fibrous web can be treated with steam, in at least some areas inside the drying zone.
Preferred design variations of the inventive apparatus are cited in the sub-claims.

r t CA 02673181 2009-06-18 For the treatment of the fibrous web with hot air, preferably at least one hot air hood is provided.
In this arrangement the drying zone can also be defined particularly through the dimensions of the hot air hood. A steam treatment of the fibrous web is advantageously conceivable inside and/or especially before the drying zone.

At least one steam blow device, especially a steam blow pipe or steam blow box is advantageously provided for the treatment of the fibrous web with steam.

The steam blow device extends advantageously at least essentially over the entire width of the hot air hood, measured across the direction of web travel.

It is also especially advantageous if the steam blow device is located at least partially inside the hot air hood.

According to one preferred alternative arrangement the steam blow device may also be located directly before the hot air hood, viewed in direction of web travel.

The steam blow device in question can moreover be arranged, designed and/or controlled so that the fibrous web - viewed in the direction of web travel - is treated simultaneously with hot air as well as with steam over only a part of the total length of the drying zone or over the entire drying zone.

If the steam blow device includes a steam blow pipe, then the diameter of the orifice of this steam blow pipe is advantageously in a range of approximately 5 to approximately I mm, and preferably in a range of approximately 4 to approximately 2.5 mm. The diameter in question preferably has an upper limit, since a certain speed is necessary for the steam jet.

If the fibrous web is covered by at least one permeable fabric, for example a permeable press belt in the area of the drying zone, then the distance between the steam blow device and the outer permeable fabric for example a press belt covering the fibrous web is preferably < 30 mm, especially < 20 mm, particularly < 15 mm and preferably < 10 mm.

If the steam blow device includes a steam blow pipe its orifices can be advantageously located from each other at a distance of < 20 mm, particularly < 10 mm and preferably <7.5 mm.

If the steam blow device includes at least one steam blow box, the moisture profile of the fibrous web can advantageously be adjusted and/or regulated through it.

If the steam blow device includes at least one steam blow pipe, the dry content of the fibrous web can be influenced or adjusted and/or regulated at least essentially through this steam blow pipe.

In principle the steam blow device may include either, only at least one steam blow box or only at least one steam blow pipe, or also at least one steam blow box as well as also at least one steam blow pipe.

If the fibrous web is covered by at least one permeable fabric in the area of the drying zone, means such as especially a doctor blade or similar devices are advantageously provided in order to remove the boundary layer of air that is carried along by the outer permeable fabric which covers the fibrous web before the fabric enters the drying area.

The hot air for the hot air hood in the drying zone can be taken at least partially from the hood allocated to a drying cylinder, especially a Yankee-Cylinder. Energy recovery of this type is possible since the temperature of the exhaust air of such a hood that is for example allocated to a Yankee-Cylinder is very much higher than the temperature that is necessary for the hot air to supply the hot air hood in the drying zone. The temperature of the hot air taken from the hood of a drying cylinder, specifically a Yankee-Cylinder can for example be approximately 300 C.
Preferably, the hot air hood in the dryer zone is supplied at least partially with hot air whose temperature is in a range of < 250 C, especially < 200 C and preferably in a range of approximately 150 C to approximately 200 C.

The temperature of the hot air for the supply of the hot air hood can be accordingly adjustable and/or controllable for optimization of the operating point with regard to the energy consumption. As a rule, a higher temperature would not result in a more efficient drying.
According to a preferred practical design variation at least one suction equipped device, especially a suction box and/or suction roll is located in the area of the drying zone, on the side of the fibrous web or the additional dewatering fabric facing away from the hot air hood.
Moreover, the suction equipped device may include especially a suction roll with a suction box that defines a suction zone.

As already mentioned, a belt press is created by an additional permeable fabric in the form of a press belt that is under tension. To this end the press belt is preferably subjected to a high tension in the range of approximately 40 to approximately 60 kN/m, in order to exert a pressing pressure in the range of approximately 0.5 to approximately 1.5 bar in a press zone. It is also especially advantageous if the length of the press zone - viewed in the direction of web travel -which is formed by the permeable press belt 80, is defined at least essentially by the area of the wrap over which the press belt wraps around the suction roll.

The length of the press zone viewed in direction of web travel, which is formed by the permeable press belt, can correspond also at least essentially to the length of the suction zone or respectively the suction box of the suction roll.

The drying zone viewed in direction of web travel can be shorter than the press zone. In certain instances it is however also advantageous if the press zone viewed in direction of web travel, is the same length as, or longer than the press zone.

The throughput volume (1/min.) of steam is preferably less than the throughput volume (1/min.) of hot air. Moreover, at atmospheric pressure the throughput volume of steam can advantageously be less than 0.5 times, especially less than 0.3 times and preferably less than 0.2 times the throughput volume of hot air.

The steam causes an increase in the temperature of the fibrous web in order to reduce the viscosity of the water in the fibrous web. To that end the steam in the fibrous web, especially the tissue web must condense so that the appropriate temperature increase can be achieved. This temperature increase may for example be adjusted through an appropriate selection of the correct temperature level for the hot air.

Preferably the temperature of the hot air treating the fibrous web is adjustable, especially for the purpose of influencing the condensation of the steam in the fibrous web.

If the temperature is too low the steam condenses immediately prior to entering the fibrous web.
This is due to the fact that the steam is cooled by the housing of the hot air hood and by the incoming colder fabrics. This could occur especially when using a so-called belt press, since the steam in this case must penetrate two outer fabrics - the outer permeable fabric, in particular the press belt and possibly a permeable structured fabric before it enters the fibrous web.

If the fibrous web is covered by a permeable press belt in the drying zone, then this advantageously has a permeability of > 100 cfm, especially > 300 cfin, particularly > 500 cfm and preferably > 700 cfm. (cfm = cubic feet per minute).

If the fibrous web is carried through the drying zone together with a permeable structured fabric, then this preferably has a permeability of > 100 cfm, especially 300 cfm, particularly 500 cfm and preferably > 700 cfm.

It is also especially advantageous if the fibrous web is covered in the drying zone by a permeable press belt which consists at least essentially of a synthetic material, especially polyamide, polyethylene, polyurethane, etc.

According to an alternative advantageous design variation of the inventive apparatus the fibrous web can however also be covered in the drying zone by a permeable press belt which is formed be a metal fabric.

Preferably at least one fabric which runs through the drying zone together with the fibrous web is pre-heated before the drying zone, viewed in direction of web travel. This is especially advantageous in the case where a press belt consisting of metal is used.

For pre-heating a steam heating device, an IR heating device and/or a hot water heating device are preferably used.

A hot water heating device is advantageous especially for an inner fabric, such as especially an additional dewatering fabric that runs through the drying zone together with the fibrous web.
As already mentioned the boundary layer of air that is carried along on the surface of the outer fabric can advantageously be removed, for example by a doctor blade which is located before the hot air hood and which extends across the width of the hot air hood. This also causes an accordingly higher temperature since it is avoided that the steam is cooled prior to entering the fibrous web. The hot air temperature can therefore be selected lower.

The current invention also relates to a machine for the production of a tissue web which is characterized in that it includes an inventive drying apparatus.

The invention is described in further detail below, with reference to design examples and to the drawings:

Fig. 1 a schematic depiction of a conventional drying apparatus which operates with steam only, as well as of the corresponding dry content increase and the corresponding temperature progression, Fig. 2 a schematic depiction of a conventional drying apparatus which operates only with hot air, as well as of the corresponding dry content increase and the corresponding temperature progression, Fig. 3 a schematic depiction of an example of a design variation of an inventive machine for the production of a tissue web, including an inventive drying apparatus and Fig. 4 a simplified schematic depiction of a modified design variation of the inventive drying apparatus, as well as of the corresponding dry content increase and the corresponding temperature progression.

Fig. 1 shows a schematic depiction of a conventional drying apparatus which operates with steam only and includes one suction roll 12 with a suction zone 10, and one steam blow box 14 in the initial area, opposite the suction zone 10. The tissue web 16 is carried over the suction roll 12 between an inside dewatering fabric 18 or felt and a structured fabric 20, together with an outside press belt which, in this example is metal. The fabrics 18 through 20 respectively are permeable. The press belt 22 is carried over guide rolls 24 and in the area of the suction zone 10, presses the fabrics 18 through 22, as well as the tissue web 16 against the suction roll 12.

The temperature T increases in the area of the steam blow box. Subsequently however, the tissue web 16 cools off drastically already inside the suction zone 10, with the taken in ambient air. As seen in Fig. 1 a dry content increase of approximately 0.2% occurs, however only in the area of the steam blow box 14.

Fig. 2 shows a schematic depiction of a conventional drying apparatus which operates with hot air only. This drying apparatus includes a suction roll 12 with a suction zone 10 and a hot air hood 26 opposite the suction zone 10 which extents across its entire width when viewed in the direction of web travel L. The tissue web 16 is again carried over the suction zone 10 of the suction roll 12 between a permeable dewatering fabric 18 or felt and a permeable structured fabric 20, together with a outside permeable metal press belt 22.

With this drying apparatus in which the tissue web 16 is dried by hot air flowing through it the dry content increase D amounts to approximately 1.5%. The temperature T
increases only insignificantly in the area of the suction zone 10 and the hot air hood 26.

Fig. 3 shows a schematic depiction of an exemplary design variation of an inventive machine 28 for the production of a fibrous web, in this case for example a tissue web, with an inventive drying apparatus 30.

The drying apparatus 30 includes a suction roll 32 with a suction zone 34 which is defined especially by an integrated suction box, and a hot air hood 36 which is allocated to the suction roll 32.

The fibrous web 38, here for example a tissue web, is carried over the suction roll 32 together with a permeable structured fabric 40, whereby the fibrous web 38 is located between the permeable structured fabric 40 and the suction roll 32. In addition, a permeable press belt 80 which is under high pressure is wrapped around the suction roll 32 on the outside in the area of the suction zone 34, thereby creating a belt press. This press belt 80 which is merely indicated in Fig. 1 is more clearly recognizable in Fig. 4. The hot air flows from the hot air hood 36 successively through the permeable press belt 80, the permeable structured fabric 40 and the fibrous web 38 into the suction zone 34 of the suction roll 32.

In addition, a dewatering fabric 42, for example felt which is located between the suction roll 32 and the permeable structured fabric 40 and through which the hot air flows into the suction zone 34 of the suction roll 32 can be guided around the suction roll 32. In the present example therefore the hot air flows successively through the permeable press belt 80, the permeable structured fabric 40, the fibrous web 38 and the dewatering fabric 42.

The moving fibrous web 38 is treated with hot air via a drying zone, whereby this drying zone can be defined at least essentially by a hot air hood 36. Moreover, this drying zone can extend for example, at least essentially over the suction zone 34 of the suction roll 32, or for example also beyond it, viewed in direction of web travel L.

According to the invention the fibrous web 38 is now treated with hot air in the area of this drying zone, and at least in some areas with steam.

To this end the fibrous web 38 may be treated with steam at least at the beginning of the drying zone, viewed in direction of web travel L. In the present example according to Fig. 3 and viewed in direction of web travel L, the fibrous web 38 is treated only at the beginning of this drying section with steam. Viewed in direction of web travel it is initially treated with steam and subsequently with hot air.

At least one steam blow pipe or steam blow device 44, such as a steam blow pipe or steam blow box is provided for treatment of the fibrous web 38 with steam. In the present example this steam blow device 44 comprises a steam blow pipe, located preferably at the beginning of the drying zone.

The steam blow device 44 can extend preferably, at least essentially across the entire width of the hot air hood 36, measured across the direction of web travel L.
Advantageously it is located at least partially inside the hot air hood 36.

As can be seen in the example depicted in Fig. 4, the steam blow device 44 may also include, for example at least one steam blow box. In this case too the steam blow box is located again at the beginning of the drying zone which is defined at least essentially by the hot air hood 36 and is located at least essentially inside the hot air hood 36. Therefore, in this arrangement too, the fibrous web 38 is initially treated with steam and subsequently with hot air.

As can be seen in Fig. 3, means such as especially a doctor blade 46 or similar devices can be provided in order to remove the boundary layer of air which is carried along by the outer permeable structured fabric 40 covering the fibrous web 38, before the fabric 40 enters into the drying zone.

In addition the machine 28 includes a former with two dewatering fabrics 40, 48 running together, whereby in the existing example the inside fabric is the permeable structured fabric 40.
The two dewatering fabrics 40, 48 run together, thereby forming a stock infeed nip 50 and are carried over a forming element 52, especially a forming roll.

In the existing example the permeable structured fabric 40 is in the embodiment of the inside dewatering fabric of the former which is in contact with the forming element 52. The outside dewatering fabric 48 which is not in contact with the forming element 52 is separated again from the fibrous web 38 subsequent to the forming element 52.

The fibrous stock suspension is fed into the stock infeed nip 50 by means of a headbox 54.

A suction element 56 can be provided between the forming element 52 and the drying apparatus 30, through which the fibrous web 38 is held on the permeable structured fabric 40 or, respectively is pressed against this permeable structured fabric 40.

After the drying apparatus 30 the dewatering fabric 42 is again separated from the permeable structured fabric 40. Moreover, a pickup or separation element 58 is provided after the drying apparatus 30 through which the fibrous web 38 is held to the permeable structured fabric 40 during the separation from the dewatering fabric 42.

Subsequent to this the fibrous web 38, together with the permeable structured fabric 40, is run through a press nip 64 which is formed preferably by a drying cylinder 60 in the embodiment of a Yankee-Cylinder and a press element 62, for example a press roll. In the present arrangement the press element 62 is for example a shoe press roll. Following the press nip 64 the permeable structured fabric 40 is separated again from the drying cylinder 60 while the fibrous web 38 remains on the drying cylinder 60. A hood 66 is allocated to the drying cylinder 60.

A vacuum box with a hot air hood 68 or similar device can optionally be provided between the suction roll 32 and the drying cylinder 60, in order to increase the sheet rigidity.

The hot air for the hot air hood 36 which is allocated to the suction roll 32 can be taken at least partially from the hood 66 which is allocated to the drying cylinder 60. The hot air taken from this hood 66 has a temperature for example in the range of approximately 300 C
which, as a rule is higher than is required for the hot air of the hot air hood 36.

As can be seen in Fig. 3 the hot air taken from the hood 66 which is allocated to the drying cylinder can be supplied to the hot air hood 36 via a supply line 70 in which at least one valve 72, especially a control valve can be located. In addition a filter 74 may also be provided, if required, in this supply line 70 for the removal specifically of short fibers, dust or similar substances. Finally, a ventilator may also be located in this supply line 70.

The hot air taken from the hood 66 which is allocated to cylinder 60 can also be mixed with cold air that is supplied through a line 76. Also in line 76 a valve 78, especially a control valve can again be provided for the cold air that is to be supplied. The temperature of the air supplied to the = CA 02673181 2009-06-18 hot air hood 36 can therefore be adjusted through the mixing ratio of the hot air taken from the hood 66 and the cold air.

Fig. 4 shows a simplified depiction of a modified design variation of the inventive drying apparatus 30. As already mentioned, in this arrangement the steam blow device 44 comprises a steam blow box located at least essentially inside the hot air hood 36, in place of the steam blow pipe. Viewed in direction of web travel L this steam blow box is again located at the beginning of the drying zone which is defined here at least essentially by the hot air hood 36.

The present design example distinguishes itself from that in Fig. 3 moreover in that in addition to the permeable structured fabric 40 and the dewatering fabric 42 or felt a permeable press belt 80 is routed through the drying zone together with the fibrous web 38, by means of which the permeable structured fabric 40, the fibrous web 3 8 and the permeable dewatering fabric 42 are pressed against the suction roll in the area of the suction zone 34.

Viewed in direction of web travel L the press belt 18 is routed around a guide roll 82 before and after the drying zone respectively through which the appropriate tension for the press belt 80 is produced.

As can be seen in Fig. 4, a relatively high temperature T results opposite the entire suction zone which in this arrangement, also defines the drying zone. Correspondingly, a relatively high dry content increase also occurs - in this instance approximately 3%.

Component Identification List Suction zone 12 Suction roll 14 Steam blow box 16 Tissue web 18 Dewatering fabric Structured fabric 22 Press belt 24 Guide roll 26 Hot air hood 28 Machine Drying apparatus 32 Suction equipped device, suction roll 34 Suction roll 36 Hot air hood 38 Fibrous web, especially tissue web Permeable structured fabric 42 Dewatering fabric 44 Steam blow device, steam blow pipe, steam blow box 46 Doctor blade 48 Dewatering fabric Stock infeed nip 52 Forming element, forming roll 54 Headbox 56 Suction element 58 Pickup or separation element 60 Drying cylinder, Yankee-Cylinder 62 Press element 64 Press nip 66 Hood 68 Hot air hood 70 Supply line 72 Valve 74 Filter 76 Line 78 Valve 80 Permeable press belt 82 Guide roll

Claims (72)

1. Method for drying a fibrous web (38), especially a paper, cardboard or tissue web, whereby the moving fibrous web (38) is treated with hot air in the area of a pre-definable drying zone, characterized in that the fibrous web (38) is treated with steam inside the drying zone, at least in some areas.
2. Apparatus according to claim 1, characterized in that the fibrous web (38) is treated with steam within the first half of the total length of the drying zone, when viewed in direction of web travel (L).
3. Method according to claim 2, characterized in that the fibrous web (38) is treated with steam, at least at the beginning of the drying zone, when viewed in direction of web travel (L).
4. Method according to one of the preceding claims, characterized in that the fibrous web (38) is initially treated with steam and subsequently with hot air, when viewed in direction of web travel (L).
5. Method according to one of the preceding claims, characterized in that the fibrous web (38) is treated initially with hot air, subsequently with steam and then again with hot air, when viewed in direction of web travel (L).
6. Method according to one of the preceding claims, characterized in that the fibrous web (38), viewed in direction of web travel (L) is treated at least essentially over the entire length of the drying zone with steam.
7. Method according to one of the claims 1 through 5, characterized in that the fibrous web (38), viewed in direction of web travel (L) is treated with steam, at least essentially only within the first half of the total length of the drying zone.
8. Method according to claim 7, characterized in that the fibrous web (38), viewed in direction of web travel (L) is treated with steam, at least essentially over the first half of the total length of the drying zone.
9. Method according to one of the claims 1 through 5, characterized in that the fibrous web (38), viewed in direction of web travel (L) is treated with steam at least essentially only within the first third of the total length of the drying zone.
10. Method according to claim 9, characterized in that the fibrous web (38), viewed in direction of web travel (L) is treated with steam at least essentially over the first third of the total length of the drying zone.
11. Method according to one of the claims 1 through 5, characterized in that the fibrous web (38), viewed in direction of web travel (L) is treated with steam, at least essentially only within the first quarter of the total length of the drying zone.
12. Method according to claim 11, characterized in that the fibrous web (38), viewed in direction of web travel (L) is treated with steam, at least essentially over the first quarter of the total length of the drying zone.
13. Method according to one of the claims 1 through 5, characterized in that the fibrous web (38), viewed in direction of web travel (L) is treated with steam only at the beginning of the drying zone.
14. Method according to one of the preceding claims, characterized in that the fibrous web (38) is treated with hot air over the pre-determinable drying zone.
15. Method according to one of the preceding claims, characterized in that the fibrous web (38), viewed in direction of web travel (L) is treated at least in some areas simultaneously with hot air, as well as with steam.
16. Method according to one of the preceding claims, characterized in that the fibrous web (38) is carried through the drying zone together with a permeable fabric, especially a structured fabric or a TAD-fabric and hot air or steam flow first through the fibrous web and subsequently through the permeable fabric.
17. Method according to one of the claims 1 through 15, characterized in that the fibrous web (38) is carried through the drying zone, together with at least one permeable fabric (40), especially a structured fabric and whereby hot air or steam flow initially through the permeable fabric (40) and subsequently through the fibrous web (38).
18. Method according to claim 17, characterized in that in the drying zone the fibrous web (38) is covered by at least one additional permeable fabric (80), especially a press belt, whereby in this case hot air or steam flow initially through the additional permeable fabric (80) or press belt, subsequently through the first permeable fabric (40) or structured fabric and finally through the fibrous web (38).
19. Method according to claim 17 or 18, characterized in that a dewatering fabric (42), especially a felt is additionally run through the drying zone together with the fibrous web (38), whereby hot air or steam if applicable, initially flow through the additional permeable fabric (80) or press belt, subsequently through the first permeable fabric (40) or structured fabric and the fibrous web (38) and finally through the additional dewatering fabric (42).
20. Method according to one of the preceding claims characterized in that the fibrous web (38) is subjected in the drying zone at least in some areas to impingement drying.
21. Method according to one of the preceding claims characterized in that the fibrous web (38) is subjected in the drying zone at least in some areas to through-air drying.
22. Apparatus (30) for drying a fibrous web (38), especially a paper, cardboard or tissue web, comprising a drying zone where the moving fibrous web (38) can be treated with hot air, especially for the implementation of the method according to one of the preceding claims, characterized in that the fibrous web can be treated with steam, at least in some areas inside the drying zone.
23. Apparatus according to claim 22, characterized in that the fibrous web (38), viewed in direction of web travel (L) can be treated with steam within the first half of the total drying zone length.
24. Apparatus according to claim 23, characterized in that the fibrous web (38), viewed in direction of web travel (L) can be treated with steam, at least at the beginning of the drying zone.
25. Apparatus according to one of the preceding claims, characterized in that the fibrous web (38), viewed in direction of web travel (L) can initially be treated with steam and subsequently with hot air.
26. Apparatus according to claim 22 or 23, characterized in that the fibrous web (38), viewed in direction of web travel (L)can be treated initially with hot air, subsequently with steam and then again with hot air.
27. Apparatus according to one of the preceding claims, characterized in that the fibrous web (38), viewed in direction of web travel (L) can be treated at least essentially over the entire length of the drying zone with steam.
28. Apparatus according to one of the claims 22 through 26, characterized in that the fibrous web (38), viewed in direction of web travel (L) can be treated with steam, at least essentially only within the first half of the total length of the drying zone.
29. Apparatus according to claim 28, characterized in that the fibrous web (38), viewed in direction of web travel (L) can be treated with steam, at least essentially over the first half of the total length of the drying zone.
30. Apparatus according to one of the claims 22 through 26, characterized in that the fibrous web (38), viewed in direction of web travel (L) can be treated with steam at least essentially only within the first third of the total length of the drying zone.
31. Apparatus according to claim 30, characterized in that the fibrous web (38), viewed in direction of web travel (L) can be treated with steam at least essentially over the first third of the total length of the drying zone.
32. Apparatus according to one of the claims 22 through 26, characterized in that the fibrous web (38), viewed in direction of web travel (L)can be treated with steam, at least essentially only within the first quarter of the total length of the drying zone.
33. Apparatus according to claim 32, characterized in that the fibrous web (38), viewed in direction of web travel (L) can be treated with steam, at least essentially over the first quarter of the total length of the drying zone.
34. Apparatus according to one of the claims 22 through 26, characterized in that the fibrous web (38), viewed in direction of web travel (L) can be treated with steam only at the beginning of the drying zone.
35. Apparatus according to one of the preceding claims, characterized in that the fibrous web (38) is treated with hot air over the pre-determinable drying zone.
36. Apparatus according to one of the preceding claims, characterized in that the fibrous web (38), viewed in direction of web travel (L) is treated at least in some areas simultaneously with hot air, as well as with steam.
37. Apparatus according to one of the preceding claims, characterized in that the fibrous web (38) is carried through the drying zone together with a permeable fabric, especially a structured fabric or a TAD-fabric and hot air or steam flow first through the fibrous web and subsequently through the permeable fabric.
38. Apparatus according to one of the claims 22 through 34, characterized in that fibrous web (38) is carried through the drying zone, together with at least one permeable fabric (40), especially a structured fabric and whereby hot air or steam flow initially through the permeable fabric (40) and subsequently through the fibrous web (38).
39. Apparatus according to claim 38, characterized in that in the drying zone the fibrous web (38) is covered by at least one additional permeable fabric (80), especially a press belt, whereby in this case hot air or steam flow initially through the additional permeable fabric (80) or press belt, subsequently through the first permeable fabric (40) or structured fabric and finally through the fibrous web (38).
40. Apparatus according to claim 38 or 39, characterized in that a dewatering fabric (42), especially a felt is additionally carried through the drying zone together with the fibrous web (38), whereby hot air or steam initially if applicable, flow through the additional permeable fabric (80) or press belt, subsequently through the first permeable fabric (40) or structured fabric and the fibrous web (38) and finally through the additional dewatering fabric (42).
41. Apparatus according to one of the preceding claims, characterized in that at least one hot air hood (36) is provided for treatment of the fibrous web (38) with hot air.
42. Apparatus according to one of the preceding claims, characterized in that at least one steam blow device (44), especially a steam blow pipe or steam blow box is provided for the treatment of the fibrous web (38) with steam.
43. Apparatus according to claim 42, characterized in that the steam blow device (44) extends at least essentially over the entire width of the hot air hood (36), measured across the direction of web travel.
44. Apparatus according to claim 42 or 43, characterized in that the steam blow device (44) is located at least partially inside the hot air hood (36).
45. Apparatus according to claim 42 or 43, characterized in that the steam blow device (44) is located directly before the hot air hood (36), viewed in direction of web travel (L).
46. Apparatus according to one of the preceding claims, characterized in that the steam blow device (44) includes at least one steam blow pipe with orifices whose diameter is in a range of approximately 5 to approximately 1 mm, and preferably in a range of approximately 4 to approximately 2.5 mm.
47. Apparatus according to one of the preceding claims, characterized in that the fibrous web is covered by at least one permeable fabric (40) in the area of the drying zone and the distance between the steam blow device (44) and the outer permeable fabric (38) covering the fibrous web is < 30 mm, especially < 20 mm, particularly <
15 mm and preferably <=10 mm.
48. Apparatus according to one of the preceding claims, characterized in that the steam blow device (44) includes at least one steam blow pipe with orifices located from each other at a distance of < 20 mm, particularly < 10 mm and preferably <7.5 mm.
49. Apparatus according to one of the preceding claims, characterized in that the steam blow device(44) includes at least one steam blow box through which the moisture profile of the fibrous web (38) can be adjusted and/or regulated.
50. Apparatus according to one of the preceding claims, characterized in that the steam blow device (44) includes at least one steam blow pipe through which the dry content of the fibrous web (38) can at least essentially be influenced or adjusted and/or regulated.
51. Apparatus according to one of the preceding claims, characterized in that the fibrous web (38) is covered by at least one permeable fabric (40) in the area of the drying zone and that means such as especially a doctor blade (46) or similar devices are provided in order to remove the air boundary layer which is carried along by the outer permeable fabric (40) which covers the fibrous web (38), before the fabric enters the drying area.
52. Apparatus according to one of the preceding claims, characterized in that the hot air for the hot air hood (36) is taken at least partially form the hood (66) which is allocated to a drying cylinder (60), especially a Yankee-Cylinder.
53. Apparatus according to claim 52, characterized in that the temperature of the hot air taken from the hood (66) of the drying cylinder (60) is approximately 300°C.
54. Apparatus according to one of the preceding claims, characterized in that the hot air hood (36) is supplied at least partially with hot air whose temperature is in a range of < 250°C, especially < 200°C and preferably in a range of approximately 150°C
to approximately 200°C.
55. Apparatus according to one of the preceding claims, characterized in that at least one suction equipped device (32) especially a suction box and/or suction roll is located in the area of the drying zone, on the side of the fibrous web (38) or the additional dewatering fabric facing away from the hot air hood (36).
56. Apparatus according to one of the preceding claims, characterized in that the suction equipped apparatus comprises a suction roll with a suction box that defines a suction zone.
57. Apparatus according to claim 56 characterized in that the additional permeable fabric is in the embodiment of a press belt (80) which is under a high tension, preferably in a range of approximately 40 to approximately 60 kN/m, thereby exerting a pressing pressure in a press zone in a range of approximately 0.5 to approximately 1.5 bar.
58. Apparatus according to one of the preceding claims, characterized in that the length of the press zone - viewed in the direction of web travel (L) -which is formed by the permeable press belt (80), is defined at least essentially by the area of the wrap over which the press belt (80) wraps around the suction roll.
59. Apparatus according to one of the preceding claims characterized in that the length of the press zone, viewed in direction of web travel (L) which is formed by the permeable press belt (80) corresponds at least essentially to the length of the suction zone of the suction roll.
60. Apparatus according to one of the claims characterized in that the drying zone viewed in direction of web travel (L) is smaller than the press zone.
61. Apparatus according to one of the claims 22 to 59, characterized in that the drying zone viewed in direction of web travel (L) is the same length or longer than the press zone.
62. Apparatus according to one of the preceding claims, characterized in that the throughput volume (1/min.) of steam is less than the throughput volume (1/min.) of hot air.
63. Apparatus according to claim 62 characterized in that at atmospheric pressure the throughput volume of steam is less than 0.5 times, especially less than 0.3 times and preferably less than 0.2 times the throughput volume of hot air.
64. Apparatus according to one of the preceding claims, characterized in that the temperature of the hot air treating the fibrous web (38) is adjustable, especially for the purpose of influencing the condensation of the steam in the fibrous web (38).
65. Apparatus according to one of the preceding claims, characterized in that the fibrous web (38) is covered by a permeable press belt (80) in the drying zone, which has a permeability of > 100 cfm, especially > 300 cfm, particularly > 500 cfm and preferably > 700 cfm.
66. Apparatus according to one of the preceding claims, characterized in that the fibrous web (38) is moved through the drying zone together with a permeable structured fabric (40) which has a permeability of > 100 cfm, especially 300 cfm, particularly 500 cfm and preferably > 700 cfm.
67. Apparatus according to one of the preceding claims, characterized in that the fibrous web (38) is covered in the drying zone by a permeable press belt (80) which consists at least essentially of a synthetic material, especially polyamide, polyethylene, polyurethane, etc.
68. Apparatus according to one of the claims 22 through 66, characterized in that the fibrous web (38) is covered in the drying zone by a permeable press belt (80) which is formed by a metal fabric.
69. Apparatus according to one of the preceding claims, characterized in that at least one fabric (80, 40, 42) which is routed through the drying zone together with the fibrous web (38) is pre-heated before the drying zone, when viewed in direction of web travel (L).
70. Apparatus according to claim 69, characterized in that for pre-heating a steam heating device, an IR heating device and/or a hot water heating device is provided.
71. Apparatus according to claim 69 or 70, characterized in that at least one inside fabric (38), such as especially the additional dewatering fabric that is run through the drying zone together with the fibrous web (38) can be pre-heated with a hot water heating device.
72. Machine (28) to produce a tissue web comprising a drying apparatus according to one of the preceding claims.
CA 2673181 2006-12-22 2007-12-20 Method and apparatus for drying a fibrous web Abandoned CA2673181A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE200610062234 DE102006062234A1 (en) 2006-12-22 2006-12-22 Method and device for drying a fibrous web
DE102006062234.0 2006-12-22
PCT/EP2007/064290 WO2008077869A1 (en) 2006-12-22 2007-12-20 Method and apparatus for drying a fibrous web

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CA (1) CA2673181A1 (en)
DE (1) DE102006062234A1 (en)
WO (1) WO2008077869A1 (en)

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EP2122049B1 (en) 2015-12-02
US8435384B2 (en) 2013-05-07
DE102006062234A1 (en) 2008-06-26
WO2008077869A1 (en) 2008-07-03
US20090283234A1 (en) 2009-11-19
EP2122049A1 (en) 2009-11-25

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